Effect Of Active Elements On The Microstructure And Mechanical Properties Of Vacuum Brazed Joint For SiC_p/6063Al Composites

SiC_p/Al composites with high volume fraction of Si C(55%~75%)is one of promising materials for the electronic package box, while the joint stability for this material has not been solved completely during its actual application.For the brazing of SiC_p/6063 Al composites with 60% volume fraction of SiC,some suitable brazing filler metal foils were produced by rapid solidification in this paper. Based on the alloy Al-10Si-20Cu-0.05 Ce, the brazing filler metals contain different Ti content, which improves the wettability of filler metals, and corresponding properties were investigated as the change of adding Ti content. What’s more, the optimal chemical composition of brazing filler metal and the relevant brazing process of SiC_p/6063 Al composite with and without Ni-plating were studied respectively. The microstructure and some properties of filler metals, brazed joints and their fracture appearances were analyzed by metallographic observation, DSC, XRD, SEM, BSE, and EDS, respectively. The main results are as follows:The brazing filler metals, which is produced by rapid solidification technology is characterized by fine and uniform grain, litter composition segregation. While their toughness decrease with the increase of Ti(AlSi)3 phase content in the filler metals. The optimum comprehensive properties of the filler metal, such as toughness and wettability,can be obtained when the Ti content is 1% through experiment.SiC_p/6063 Al composites with Ni-plating were brazed with the filler metal foil containing 1% Ti content, and the shear strength of their brazed joints increased at first and then decreased with increasing the brazing temperature or prolonging the soaking time. What’s more, some small block SiC particles migrated and accumulated in the seam under higher temperature or longer soaking time, leading to the destruction of joint compactness. With the optimal brazing process of 8 × 10-4Pa vacuum degree,50 min and 590℃, the good joint with compact microstructure was obtained. Its shear strength achieved to 121.3MPa and the joint had a ductile fracture occurring in the filler metal layer.As the nickel layer deposited on composite, the wettability of filler metal was improved significantly. When this kind of SiC_p/6063 Al composites were brazed by fillermetal containing 1% Ti, a good joint was obtained as well, and its optimal brazing process is vacuum degree 8 × 10-4Pa, soaking time 50 min and brazing temperature590℃. Due to the sufficient interactions between filler metal and composites, the shear strength of the brazed joint could reach to 113.5MPa,and the fracture is characterized by brittle.After the comparison between optimal brazing process for SiC_p/6063 Al composite with and without Ni-plating, it is clear that priority to select the brazing process with Ni-plating should be taken considering the actual productivity and cost, whose joint shearing strength has satisfied the use requirement.